Modulated light projector with scrambling drive



Feb- 2, 1954 D. E. HooKl-:R ETAL 2,668,230

MODULATED LIGHT PROJECTOR WITH SCRAMBLING DRIVE Filed May 28, 1948 4 Sheets-Sheet l X7-z en fo r6.'

/ l y- F eral caidas Feb- 2, 1954 D. E. HOOKER ET Ax. 2,668,230

MODULATED LIGHT PROJECTOR WITH SCRAMBLING `DRIVE! Filed May 28, 1948 4 Sheets-Sheet 2 Ilillllillllllllllllllllll/lI/ Feb. 2, 1954 D. E. HOOKER ETAL MODULATED LIGHT PROJECTOR WITH SCRAMBLING DRIVE 4 Sheets-Sheet 3 Filed May 28, 1948 3 9 .Sow/Dik (cola Feb- 2, 1954 D. E. HOOKER ETAL 2,653,230

MODULATED LIGHT PROJECTOR WITH SCRAMBLING DRIVE Filed May 28, 1948 4 Sheets-Sheet 4 reflector and lens Patented Feb. 2, 1954 MDULATED LIGHT PROJECTOR. WITH SCRAMBLING DRIVE Donald E. Hooker, Skokie, and Frank G. Nicolaus, Chicago, Ill., assignors to Raymond T. Moloney,

Chicago, Ill.

Application May 2s, 194s, serial No. 29,876

(o1. 24o-4s) 12 Claims.

This invention relates to photoelectric apparatus and the use of modulated light in conjunction with selective photoelectric circuits, and controlled means operated thereby responsive to the discriminative operation of the photoelectric circuit when actuated by appropriately modulated light. v

The important objects of the invention pertain to the provision of a projector of modulated light in the nature of a compact unit which includes a light source, modulating means, manually and automatically operable means for directing the light pattern at will or in accordance with a variable or scrambled pattern, and circuit connections and controls appurtenant thereto.

A previous, copending application, Serial No. 378,645, filed February 12, 1941 by Donald E. Hooker, now Patent No. 2,516,319, discloses photoelectric marksmanship apparatus utilizing a form of modulated light as part of a discriminative system.

The present application pertains to apparatus useful in conjunction with the disclosures of U. S. Patent No. 2,442,240 to Donald E. Hooker et al.

In its more detailed aspects, the instant application is directed to details of the construction and operation of the light projecting unit and means, and control circuits therefor, including particularly a rockable housing fora system, a hollow rocking axis member for the housing, a light source aligned with the hollow axis, modulating means affecting the light through the hollow axis, together with pivotal mountings and manipulating appurtenances by which the housing may be directed to throw the modulated light variously on a wall, screen, or other surface to cause a marksman to exercise skill in following and taking aim at the target defined by such modulated light.

Additional details of novelty in the invention relate to the control circuits for automatically meandering the light beam through a plurality of motor drives for moving the housing with respect to several pivotal vor turning axes, for varying in uncertain manner the rate of movement with respect to either turning axis, for reversing such movement at irregular times, and for scrambling in indenite pattern the changes in rate and direction of the aforesaid projector movements.

Further objects, advantages, and `aspects of novelty vand utility in the devices and methods hereinafter disclosed, pertain to structural and functional details of the commercial embodiment of the marksmanship training and testing apparatus described hereinafter in view of the annexed drawings'in which:

Fig. 1 is a perspective of the projector unit with the cover removed; y

Fig. 2 is a horizontal section through the horizontal axis of the projecting unit of Fig. 1;

Fig. 3 is a vertical sectional fragment of the lamp housing shown in Fig. 2;

Fig. 4 is a perspective view of the pick-up or light gun with the cover removed and portions of the mounting brackets broken away;

Fig. 5 is a perspective of the projecting table with lower portions of the legs cut away, showing the projector and amplier units mounted thereon;

Fig. 6 is a schematic diagram of a modified form of projective arrangement and circuit connections for the photoelectric gun and score counting means;

Fig. 7 is an elevational view of a variator for the image forming means;

Fig. 8 is a graphical representation of the wave form of the amplified and rectified signals in the photoelectric circuit, representative of the double-modulated light tuning means of the invention:

Fig. 9 is a perspective of a modied form of projector with power driven meandering means; Fig. 10 is a circuit diagram for the projector of Fig. 9;

Fig. 11 is a detail of the bler drive.

In its more general aspects, the invention is best explained by reference first to the schematic showing of Fig. 6 herein, in which there is shown a light source I5 which projects light through an image forming device i 6 adapted to be moved by a cam arrangement Il (see Fig. 7 also) driven through a train of gears I8 by a motor I9. In the present instancethe image forming device I6 is designed to dene the image of an airplane, which image is adapted to be projected on a reflecting surface, such as the screen 25 or a wall surface or the like, the light rays which dene such image being reected from a dirigible reecting device or mirror 23.

The image-forming rays from source l5 are modulated or keyed by a special form of interrupter disc 20, which (see also Fig. 8) includes a group of serial holes 2 l, in this instance four in number, alternating with elongated slots 22 adapted to provide a peculiar modulation, which for present purposes may be referred to as double modulation. and which is most conveniently interpreted in terms of the resultant amoled signal or amplifier! photoelectrmiznpulse wave forms shown in Fig. 8, wherein the wave form or component A represents the first or principalmodulation (after amplication) efected upon the llight which is permitted to pass by any given group of small holes 2l, while slip clutch and scramthe smaller wave component B represents the second modulation due to the slots 22, with an obviously ,lesser `frequency amplitude .than .those caused 'by the series of fholes.

Regarded in another aspect, the Wave components A and B may also be considered to represent the output signal of the photoelectric device after amplication by amplifierlter-conversely the input signal as received by the detector or rectier, While the third AWave.iorm C .in :Fig represents the rectied signal -.o f predetermined frequency delivered at the output of the main arnplifier for purposes of operating a score control device or the like.

For present purposes, it is suiicient to state f that the disc 2B is rotated at a speed correlated to .the sizeandspacing of .the modulatingorllightkeying formations, that .is .the "holes and slots, which willcause .the light beam Vto .be 'interrupted at a principal .frequency .of 1920 timesperfsecond .(byQholes .211, ,and .at a secondary or .superirn posed frequency of i240 times .per second '(byslots 12).. The peculiar .advantages Y'flowing Afrom .this arrangement -Will he discussed Shereinaiter.

Referring again to .Fig. T6, there jis .additionally .provided a'background.projectingmeans such as va .moving picture A,prmector lli .adapted .to project suitable 'background .scenery 215e onto .these-reen `25 as'indicated below the dotted'line ZLtlleiniage .Ilia of the airplane .being indicated above .the

'dotted'.linc. The 'imagemaybe vmoved about atwill over the background 'images Without intererence from the latter.

lThe arrangement .further includes an aiming device or gun 3'0 preferably .provided with an ohjective .lens 3| adaptedto .collect the target image rays from screen 25 fo11passage'through-anapertureplate 32 and onto aphotoelec'tric cell '3.3 con- `n'ected ,with a pre-amplier 3.4 which is housed in the gun 3U and which is peaked or tuned to 1920 cycles. The pre-,amplifier .has .its output connected to a main detector-arnplifier unit .3.5, [including adetector or rectineriDET.,.and anramu plier which Vis discriminative ,for tmaximum .output at ,about 240 .cyclesper second.

Tho amplifier output is connected to .a ,oo ntrolled instrumentality, such as vthe hit relayfii, which .in turn controls through itslswitch .31 ,an electrically operated hit Aor score counter 138 `of known construction.

YIn order toprovideia realisticeiiect, an electrically operatedshot sounder-'39 of'known construction is connected for operation from a power supply orbattery M- under control of a nre'switch or Itrigger E@ which completes a power circuit `to g' the shot sounder from a commonlorground connection Gthrough contacts 513i, conductm L52 and 'interrupter earn switch i3 to the sounder'a and 'via'conductor t5 .to battery )4.4.

An 'interruptermotor 68 drh/:esa cani '4J vto :etfect opening and Vclosing'of switch 43 vat a desired vHiringrate of 850 times 0er minute, While another carn 58 opens and closes a supervisory switch 49 at the same rate to intermittentlyeonneet both the shot counter land'hit counter 38 (through hit relay switch '37) with the power source or battery 'M via vconductors 5l and a5.

As a result of the foregoing arrangement, it will'appearthat it is necessary that trigger switch lill-M 'be closed in order to conditi-on'thehit and shot counters for operation and to actuate .the sound-'effect device 39, andthat these control vcircuits are Ainterrupted at arate of '8,59 times per minute by the interrupter cam switches.

If the gun 30 were 4properlyvtrained upon the -1 4 luminous target image Ia for the duration of a minute, a perfect score would be registered, indi- .catinglS-O shots on thas'not-lcounter-l and 850 hits on .the hit 'counter 3S. T-:Vhen the target is moving, of course, the marlrsmans skill in keeping the Weapon trained during the intervals when the 'trigger is pulled, is measured by a comparison of fthe readingsof lthe hit counter 38 and the shot counter 46.

.lymodulating .the light employed to denne a ,target image .-such as the image of the airplane Ita, Fig, and-.by'tuning the ampliers 34 and 35, or either of them, to the frequency of the modulation, th'e'sys'tem is rendered highly selective, so

f lthat'zitfis not only possible to use the device in the presence oi extraneous modulated light, such as .that supplied by .incandescent .lamps from `the usualalternating current .mains Lordinarily 'interrupted '120 `times per second) but .in .addition .lit Lis ,possible to deliberately project .variably modulated light, as bythemotion picture projector ".25, with :such alhigh .degree of selectivityin .the pickup device' andthe associated amplifying means, .that .the rlight fluctuations caused by `the motion picture ,projector .26 .or .analogous device, in lno .way .interfere with .the proper .operation -of .the photoelectric .means -even `4though they may ,contain .random component .frequencies .o Athe modulation .frequencies .Thus .liaise indications .of .a vhit -by .the .counting .device '38 :are obviated, .and lthe ,adaptability Aof the .system as .a .Whle .is .vastly extended.

,In .accordance with the ,present invention both xthe .selectivity andthe sensitivity of .the photoelectric system have vbeen greatly increased Loy contriving' .a .certain .kind of modulation, .which ior purposes .of present disclosure, is .referred Yto as double modulation. 'This 'is conveniently `err-- Aplained by .reference to Fig. T8 wherein .there is shown one .of 'the .modulating .discs T23, .and immediately thereabove a graphical representation of the approximate variations in projected light (and hence .in the 'electrical impulses or signals resultantly vstimulated thereby in the photoelec- `tric means Bil-234).

It will be further observed 'from Fig. 8 that `dotted-line projections have been :extended 'from 'the uppermost .elongated slotl 22:6 to Athe 'smallamplitude Wave vlines 'indicated at 'B v'thereahoya While dotted lines extend .from :the two lianking groups of holes 21u: upwardly to 'the correspondinghig'h-amplitude portions A of the wave representation.

'In Vthe :foregoing illustration, it will be appreciated 'that `during .that portion of the rotation `of :the modulating disc 20 when the 'holes v21:1: 4are `passing `before the projecting aperture, the .projected light will .be ,interrupted rapidly with :relatively 'small amounts o'f 'light passing through Vas 'each of the small .'ho'les .cuts across the light path, 'but when the relatively lopen elongated slots l22a: out across the light path, a considerably larger amount of light is permitted 'to `pass 'and the frequency of .interruption drops as `shown graphically Aby the component B of the Wave-form representations. 'The resultant rectified impulse which leaves the main amplier unit 35 to operate the `controlled .instrumentality or hit counter relay 36,'has .the wave `form represented at C of Fig. 8, which `form is ,particularly .effective for its `intended purpose, and is made possible by the original double .modulation A-LB .resulting from special modulating formations 21-22.

In other terms, the .dual mo. ulation'increases lthe discriminative action of the device since the pick-up can be tuned to both modulating frequencies; for example, the pre-amplifier 34 in this case is tuned preferably to 1920 cycles, while the second main amplier, AMP., following the detector, DET., may be inexpensively tuned to the frequency of the rectified or detected impulses-in this case, preferably 240 cycles.

Since the methods of tuning such amplifier circuits are well known in the art and do not constitute per se the invention herein, the specie circuits are not described in detail.

The pick-up or gun 30 is shown in detail in Fig. 4, and includes a box-like housing 30a mounted on support bars 30h, and provided with a barrel portion 30e in the front end of which is a. telescoping lens mount 30d carrying a collecting lens 3 I.

A light spot focusing plate 30e is slidably and rockably mounted by means 30j to the rea-r of the barrel in front of the photo cell 33, and the .plate is pulled toward the right by a spring 30g against an azimuth adjusting set screw 30h, and also downwardly against a zenith adjusting set screw, 307 (dotted lines), by means jof both of which the light aperture 30k in the plate may be adjusted with respect to the photo cell 33.

Pre-amplifier elements or tubes 34a and 34h. and tuning choke 34o are also situated within the gun housing and adapted to be connected with the main amplifier unit 35 by a cable lead 34d leading to the control table 59, shown in Fig. 5 upon which the projector unit 60 and main amplifier unit 35 are mounted.k The gun housing shown).

The projector As viewed in Figure 1, the projector consists of a base 6I, upon which is mounted a hollow turret plate casting s2 to swivel about a hollow shaft 63. Upon a bed plate 64 is mounted an upright bracket 65 constituting one of a pair of trunnion members for a rockable lens and projection housing 6l, the other trunnion member being a small plate 66 mounted (see also Fig. 2) on the side wall of a lamp housing 68. Plate 64 constitutes a cover for recessed parts 62C, but is spaced from the top of the turret casting by washers 64X to provide for ow of air relative to the hollow parts of the base structure.

At one (left) side the lens housingpivots on a pin 69 in bracket 65, while at its opposite side it pivots upon a bushing 10 (Fig. 2) seated in plate 66 and fixed in the end of a tubular extension 'H secured to the lens housing in alignment with its rocking axis. (See also Fig.v 3.)

Referring to Fig. 3, the lamp well or housing 5B is seated on the bed plate 64, and includes a lamp' socket 66a mounted. on posts 68712 by screws 68d threaded into bosses 62a on the turret plate just above a hollow air-flow passage 62o formed in the turret plate. Air passages 64a are provided in the bed plate for air driven by a fan I2 driven by small motor I3 (dotted lines Fig. 2), so as to cool a powerful electric lamp '14. The top of the lamp housing is open and provided with cooling louvres (Figs. 1 and 3).

A handle 67d projects from the rear of the lens h housing for manipulation by the instructor.

At the front of. the housing is a cast lens mount or frame '.'ib (Fig. 2) in which are mounted a pair of condensing lenses 6'Ic in alignment with a reflecting mirror 23 secured by brackets 30a is normally closed by a cover (not 61d across the interior of the lens housing in the path of light from lamp I4 passing through an aperture 68e in the lamp housing, so as to redirect the light at right angles to its original path of projection from the lamp housing. A rubber buffer or stop collar 67e is mounted on a tie rod 61j joining bracket 65 and housing 68 to cushion upward or zenith movements of the projector housing, while another stop 61g on post l stops downward motion thereof.

A very important feature of the invention is the modulating disc 20, which is fast on the shaft 26a of a small synchronous motor 20h secured to a mounting plate 20c fastened as at 20e to the bed plate. A bale 20] serves to direct air from the hollow turret plate through one of the openings 64a to cool this motor. The small holes 2| and slots 22 of the modulating disc pass in optical alignment with the aperture 68e in the lamp housing, and bushing "I0, so as to interrupt the light to be reflected from mirror 23 as heretofore described. l

As viewed in Fig. 5, the projector is provided with a cover or hood 60a fastened onto the turret plate as at BDI), and includes an arcuate window 69e before which the lens housing can rock.

The form of projector just described is rocked up and down and sidewise by manipulation of handle 61a by the instructor, who is positioned before the table 53, while the marksman manipulates the gun 30 and endeavors to follow the target image of light as it is cast about the walls or onto a screen 25 by the instructor. If desired, the aperture 66o of Fig. 3 may be shaped to dene the outline of an aeroplane, tank or other object of warfare, or an image-defining plate such as the plate I6 (Fig. '7) may be interposed in the path of the light rays before interruption by disc 20. The image plate I6 may be mounted in slide brackets I6a for both vertical and horizontal movement by a harmonic cam I6b working in a square (or otherwise designed) cam hole in plate I6 to cause the outline to move with a complex motion. The motor I9 may be used for this purpose with a train of gears I8 interposed.` It should be understood that the size of the openings 2I and 22 is dimensioned to correspond to the size of the aperture 68e or the image-defining outline of the aeroplane, the latter being somewhat exaggerated by size in Fig. 7 for clarity.

Power driven meandering means In Fig. 9 there is shown a modified form of the projector of Fig. 1 wherein power-driven meandering means is substituted for the manual control. To this end, there is provided a small motor mounted on bracket 65 and arranged to drive a worm BI through a speed reducer 82 toslowly drive a pinion 83 fixed on the rockshaft 69 of the 'lens and projector housing. l.

Another small motor 35 seated on the base plate is likewise provided with a speed reduction unit 86 driving a worm 87a, which in turn drives a pinion 8? fixed to rotate the shaft 63. Motors 8u and 85are connected to a special control cir'- cuit which reverses them at appropriate intervals, and also varies their speed in a scrambled manner to produce irregular meandering of the projector.

In Fig. l0 there is shown circuit means forY meandering the projector, which includes the two motors 80 and 65 connected with reversing relays and commutating control switchesiand a scrambling device. Motors S and 85' are connected in the saine manner to have their speeds varied by 7 cutting 1in resistance, :and 'to :ne :reversed :by .re- -rversin'g relays.

fIrhe .illustrative :arrangement of Fig. vlo provides :a connection sfriorn power terminal 'et via fconductor 92 `toiield terminal :S3 'of fmotor SG, -f

and 'via =conductor 913 tosiield .terrninal' Aoi imo- 'stort-:85.

A .reversing .connection ais effected 'from 'eld :terminal -96 .of fmot'or .85 via LYconductor '-91 to .a commutatorfswitch wiper JBti-.adapted tc-succes- :sively rcngage -contacts LS9 each Aconnected to a .fresistance fl. .This eld circuit .is =completed avia conductor `r|||| toxcontact-s |2 |33 ona'fre- Nersing :relay having: amovabie contact 6'4 which .engages Anormal contact |02 lwhen `the relay is :dropped out. Contact |l`|is connected to'motor :brush edv-and y'thiscircuit iscompleted from Vthe iother .brush it viaimovablecontact iti' and its :normalicontact ;|i8,;power:lead :las andhack to power terminal :9 I, so thatfmotor '.65 will' run in a certain direction andv at Ivarying speeds` depending on the passage of Wiper'contact't -intoand lroutof engagement with resistance contacts 99.

:Motor 85 will be :reversed -by energizaticn o winding IB of its reverse relay from :conductors 94 and H0, .the latter connecting with a rotary fwiper adapted to engage in succession looped ycontacts i112 `on :the corresponding 4commutator .'switch .and which are-connected tothe remaining .power lead M19 by .conductor i3.

Relay Winding B ,Willremainenergized so long -as wiper .engages'acontact H2 Vconnected to ,power lead |09, and I.will :reverse the connections `Jcetvveen.brushes l5- |06 tand eld coil terminal `56. By varbitrarily connecting contacts H2 in random order Ato v.the ,power line, :the reversing relay B `may be operated 'to cause reversals `at yirregular intervals thus scrambling Vthe com- ;ponent of motionof fthe projector-contributed hy 'motor .Exactly the fsame kind of a reversing circuit :is supplied for motor t6 under control 'of :reversing relay A, and Ait is therefore i-believed unnecessary .to repeat -the explanation 'of the duplicatecir'cuit connections shown -in Fig. l0 for motor 8|).

Scmmbling control `Means Vfor Yfurther rendering irregular "the Vopveration o'f the `aforesaid meandering or scrambling control for 'the Aprojector includes a driving motor |50 (Fig. lo) for the several commutator switch Wipers 98, |55, i i6, fior both motors 8|) and 85. This motor |50 drives a variator disc 54 having notches |52 of irregular length cut in its periphery. A springy brake arm |53 is arranged 'so 'that its, offset end |513 rides von said periphery into and out of the `notches thereon. (See also Fig. 11.)

' In axial alignment `with 'disc |5| is 'a driven member or pin disc |55 having a plurality of axially projecting pins |56 projecting from its face toward the variator disc and so arranged as lto strike against the 1crake arm |53 when the latter is bearing as far as it can toward the variator disc'by virtue of the oiset I riding in one of the notches |52, in which position the brake arm is disposed in the path of the pins |56. As soon as the ofset nose IEA of the bra-he arm rides out of a notch onto the normal periphery, the brake arm is sufficiently withdrawn from the path of the pins topermit the pin disc |55 to rotate freel n, which it Will do'through the `agency of Aa special slip `clutch 51.

*Slip 4clutch |51, as shown in Fig. il, 'consists simply 'of 'a'metal *spring Washer or spider |5la randsalternate metal Fanriifelt washers 151D, 11i-tlc, the latter being firm" lypushed yagainst. the itacc :of pin r,disc '155 xby action 'of 'the spider washer |5ia, that the .fpin :disc 'tends to -be ncarried 'around 'with' the variator ldisc owing to Ifrictional drive Aafforded by the :telt iwasher, `although fa -sufcient.resistance,fsuchfas blocking .o'f Apins t by thebrake .arm y| 53 would :restrain "the -pinfdise Tin disc :|55 is lcorme'cted'ioy `.the dashdotline i ito .drive .the icommutator switch wipers '88, a||5, .|:|6.for varying fthefspeed `anddirection of rotation.ofrtheprojectorcmotors iandifand :since 'the "notches |52 -are icut irregularly in the lvariator disc, :and Ipins |58 are fset irregularly (With :respect to .circumferential spacing 'relative cto ieach iother) lit 'will bc :apparent that pin 'disc |55 and hence the drive -connection |63 iior=th`e commutating switches will be started -and stopped in aan :irregular fashion, thus causing motors 8U zandfl to .operate lrregularly,rand 'thus scrambling or rendering .relatively .uncertain the nrovementst'of :the target-image i'apetc.

lThe 'objects aand advantages Tof the invention vmay also 'be realized by modifications 'in 'the V:specific illustrative construction and far-range- -ments disclosed herein, fand it 'is the intention that all such :modifications and equivalent arrangements :shall ;be included in theinvention as -fdened'.inztherappendedfclaims.

Weicla'im:

-:1.:A ylight jprojec'tor :comprising a base and :means mounting 'the same 'for rotativemoveinent about a vertical axisandlhavingan upright lamp housing near vone iside -1of :said ibase, an upright trunnion plate nearian opposteside of vsuitcase, a chamber having on one side thereof pivotal support on said platezand having attached to an opposite side thereof a tubular arm pivotally supported on 'said housing for '-p'ivotal 'motion labout a horizontal axisthrough'said arm, there 'being a Vlight passage Ein the housing faligned with said horizontal -axis through the tubular arm, a reec'tor in said 'chamber directing lig'ht 'a't 'substantially right angles to said yhorizontal axis out df the chamber, "said tubular 'armrotating `with lsaid 'chamber relative to said horizontal axis.

f2. A projector' -in accordance LWith 'claim '-1 'and further-characterized by th'eprovis'ion of 'a' motordriven interrupter disc mounted to rotate in a plane transverse of V'said 'horizontal axis between saidhousing passage and'tubular arm across the path -of light therethrough.

I 3. A projector in accordance with clam'2 'and further characterized by the `provision of Amotor meansfgearedto saidpivotal mount of the 'chamlber to lpivot lthe chamber `'on said horizontal'aiis motor means on said base geared to pivot the latter about said 'vertical axis, and 'a scrambling Vpov/'er `circuit for Yboth said motor means to 'impart `irregular motion to 'said 'chamber 'and base with respect to 'components of Aboth speed and direction, said circuit 'including power-operated 'automatic current-varying and switching means connected 'With'said motor means for the 'purpose aforesaid.

l4. In a device ofthe class "described, Scrambler means Afor 'controlling irregular vcircuit connections `and comprising rotary switch 'means .for changing connections in said circuit -to beicontrolled, -`a motor to drive 'said switch rotatably, a'slip clutch between said motor .and switch, .cam means vdriven by 'saidmotor .on the motor Mdrive side 'of said clutch, 'said cam means, l.having :a 4plurality 'of :irregular "cam dwells, brake means including a brake arm yieldingly urged into braking engagement with a brake member on the driven side of said clutch associated with said switch, and means on said brake arm riding the cam dwells cn said cam, whereby the brake means is irregularly applied and released to effect irregular rotations of said switch. y

5. A light projector comprising a horizontallyextensive base member having a hollow portion, and means mounting same for rotative movement about a vertical axis, an upright lamp housing mounted near one side of said base and having an open top portion and a bottom opening communicating into said hollow portion of the base, a blower including a fan rotatable about a vertical axis in said hollow portion of said base to displace air through said bottom opening and open top of the lamp housing, an upright trunnion support xed for movement with said base opposite said housing, a chamber trunnioned by and between said support and housing to rock about a horizontal axis therebetween, there being a light passage from said housing into said chamber aligned with the rocking axis of the latter, aforesaid, and reecting means in said chamber directing light from said housing at substantially right angles to said rocking axis outwardly of the chamber.

6. In apparatus of the class described, an optical projecting device mounted for movement with respect to both vertical and horizontal axes, separate electric motor means for moving said device with respect to both axes aforesaid, rotary switch means for varying operating currents for said motor means, and scrambling means including a motor to drive said rotary switch rotatably, a slip clutch between said motor and switch, cam means driven by said motor on the motor drive side of said clutch, said cam means having a plurality of irregular cam dwells, brake means including a brake arm yieldingly urged into braking engagement with a brake member on the driven side of said clutch associated with said switch, and means on said brake arm ridingthe cam dwells on said cam, whereby the brake means is irregularly applied and released to effect irregular rotations of said switch.

7. In a dirigible light projector, a hollow horizontally-extensive, upwardly-open base pan, and means mounting the same on a pedestal for rotative motion about a vertical axis; a base plate mounted over, but spaced above, the opening of said pan to substantially close the same and dene a chamber interiorly of the pan with an air passage afforded around the base plate by said spacing; an upright lamp housing mounted on said base Iplate at one side of said Vertical axis and having an air passage communicating at the lower part thereof through said base plate into said chamber, an upright member carried on said base plate on the opposite side of said axis from said housing; an optical chamber having a first pivot support on one side of said upright member and having xed on its opposite side an elongated tube axially aligned with the axis of said pivotal support and projecting in close proximity to said lamp housing; a spacing member secured on a side of said lamp housing in spaced relation away from the latter toward the proximate end of said tube; a tubular member constituting a second pivot secured to said proximate end of the tube in axial alignment with said rst pivot, and having pivotal support on said spacing member; a coaxial light passage formed through the side of said housing and the appertaining spac- 10 ing member in alignment with the axis through said rst and second pivots; light re-directing means in said optical chamber in optical alignment with said coaxial light passage to receive light from a lamp in said housing and redirect the same at an angle to the coaxial axis; and fan means carried by said base plate for drawing air into said base chamber and forcing same up into said lamp housing.

8. A projector construction according to claim 7 and further characterized by the provision of a motor-driven light modulating disc carried by said base plate and rotating in a plane across said coaxial light passage at a position between said spacing member and said lamp housing.

9. A construction according to claim 7 in which said fan means includes a rotatable impeller disposed beneath the base plate in said base chamber, and a driving motor therefor carried on the upper side of said base plate.

l0. A construction according to claim 8 further characterized by the provision of a rocking motor mounted on said upright member and drivingly connected with said rst pivot means for rocking the optical chamber; and a second or turning motor carried on the base plate and drivingly connected with said hollow base member to turn the same; together with motor driven circuit means connected With said iirst and second motors for concurrently varying at least the speed of both said last-mentioned motors.

1l. In light-projecting apparatus, an optical projecting device mounted for movement with respect to at least two axes; separate electric motor means for moving said device respectively in each of the two axial movements thereof; variable-current control means for varying the speed of said motor means and including a motordriven speed-,change switch operating to selectively and progressively connect diierent current-limiting means in an operating circuit for said motor means whereby to produce a variablespeed compound motion of the optical device relative to said axes, together with intermittentactuating means cooperable with said speedchange switch to render the operation of the latter irregular.

12. Apparatus as dened in claim 11 in which said separate motor means are reversible, and said control means includes reversing switch means connected thereby intermittently in said operating circuit whereby the motion of said optical device is varied in respect of both speed and direction of operation.

DONALD E. HOOKER. FRANK G. NICOLAUS.

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